The present invention relates to an image processing method applicable to recording of images of a color document or color video signals and, more particularly, to a method and apparatus for compensating for color distortions which are contained in inputted original color document images or color video signals.
When original color images are scanned by a color scanner, for example, there is produced red (R) data, green (G) data and blue (B) data where the signal levels are individually associated with the color components of the images. Theoretically, the original color images may be reproduced by mixing cyan (C) ink, magenta (M) ink and yellow (Y) ink by subtraction using the scanned R, G and B data. In practice, however, a scanning system involves various kinds of distortions such as the distortion caused by the spectral transmission characteristic of a filter which is included in a color scanner for color separation. A recording system also involves distortions such as is caused by the coloring characteristics of ink, the gamma characteristic attributable to the dot printing ability of a printer and the representation of half-tone which relies on a matrix of dots. Distortions may also be due to the use of different kinds of papers. Such distortions are combined together so that, generally, a reproduction does not accurately conform to the subtraction color mixture. For this reason, color compensation processing has customarily been employed.
Prior art color compensating methods are elaborated in regard to a color copier or like color image recording system for example, in Japanese Laid-open Patent Publication (Kokai) Nos. 57-131172 and 57-101840. The problem with those prior art methods is that they simply process colors such that input and output colors correspond on a one to one ratio to each other and therefore the original colors of a document are reproduced with fidelity.